A new study has found that obese fathers up risk of autism in their offsprings more than obese mothers.
Dr. Pal Suren from the Norwegian Institute of Public Health, who is the first researcher to study the role of paternal obesity in autism, and his fellow researchers used data from the Norwegian Mother and Child Cohort Study (MoBa).
The researchers studied questionnaire data from over 90,000 Norwegian children at three, five and seven years of age. The mothers had answered detailed questions about their own mental and physical health, and about their children.
The fathers completed a questionnaire about their mental and physical health while their partner was pregnant.
The researchers also collected data from the Norwegian Patient Registry and from studies of children who were referred for evaluation and treatment of possible autism or Asperger's syndrome. By the end of the follow-up period, the children were aged 4 to 13 years.
The findings showed that 419 children, approximately 0.45% of the sample, had an autism spectrum diagnosis (ASD).
This is slightly lower than in the general population (0.8%) because it is difficult to diagnose autism among the youngest children.
In the sample, 22% of the mothers and 43% of the fathers were overweight, with a body mass index (BMI) of between 25 and 30.
Approximately 10% of mothers and fathers were obese, with a BMI of 30 or more.
The researchers found that maternal obesity had little association with the development of autism in the child. However, they found a doubled risk for development of autism and Asperger's syndrome in the child if the father was obese, compared with a normal weight father.
Suren said that he and his team were very surprised by these findings because we expected that maternal obesity would be the main risk factor for the development of ASD.
"It means that we have had too much focus on the mother and too little on the father. This probably reflects the fact that we have given greater focus to conditions in pregnancy, such as the growth environment for the foetus in the womb than both environmental and genetic factors before conception," Suren said.
The researchers adjusted for variables that may also be associated with the development of autism in the child. In addition to adjusting for maternal obesity, they considered education, age, smoking, mental disorders, hormone therapy before pregnancy, use of folic acid, maternal diabetes , pre-eclampsia and the baby's weight at birth.
The researchers found that the risk remained unchanged when adjusted for sociodemographic and lifestyle factors.
Suren said that the findings suggest that there may be a genetic link between obesity in the father and the development of ASD in the child.
Researchers are still in the early stages of studying possible links between obesity in the father and the development of ASD in the child.
The study is published in the May issue of Pediatrics journal.